This invention relates in general to the transfer of rotary motion an more particularly to a traction drive unit for transferring such motion.
Several varieties of transmission exist for transferring rotary motion at both fixed speed ratios and variable speed ratios. Perhaps the most common is the so-called gear box in which the rotary motion is transferred through intermeshing gears. But gears with their teeth require extensive machining operations to form and thus are expensive. Moreover, they can be noisy and set up vibrations. Gears inherently contain backlash and are somewhat less than totally efficient.
Friction or traction drives, which rely on the friction between smooth contacting surfaces to transfer torque, possess some of these disadvantages, but at a lesser magnitude than gear boxes. In this regard, traction drive units require less complex machining and transfer the power smoothly and quietly. Moreover, they have the capacity to transfer power at extremely high velocities. They operate with no backlash and at high efficiency. Even so, the better friction drives are bulky and contain a multitude of rollers and other parts which are especially adapted or configured for such drives.
The present invention resides in a traction drive which has its components organized into a planetary system. In spite of this, the drive is highly compact and operates with high efficiency.